Reasserting the Utility of Obsidian Hydration Dating: A Temperature-Dependent Empirical Approach to Practical Temporal Resolution with Archaeological Obsidians

Abstract

In a recent paper in this journal, Anovitz et al. (1999) identify potentially serious flaws in the measurement and modelling of obsidian hydration for dating archaeological obsidians. This critique follows other recent papers highlighting potential problems with the method (e.g., Ridings, 1996; Stevenson, Mazer & Scheetz, 1998). Contrary to this latest critique, the current paper offers evidence for the apparent efficacy of a quadratic model for obsidian hydration dating of archaeological obsidians, using empirical results from archaeological projects throughout the western United States. It is posited that this model is sufficient, in part, due to limits of commonly used methods of hydration analysis, which also provide a cost-effective means for large-scale sampling. Given apparent support for quadratic modelling and, hence, the diffusion theory underlying it, an empirical approach to obsidian hydration rate formulation that incorporates field temperature data is explored. Although evaluation of the resulting rate formula for Casa Diablo obsidian is somewhat equivocal, the results are relatively robust when compared to other posited rates. As such, the approach appears to hold promise within the limits of temporal resolution necessary for many regional research strategies, while also serving as a potential check of laboratory-based strategies.